"Visitors and members of the public took leaflets and tooted their support – there was no antagonism at all," said Tony Hammond, Prospect negotiator. "The overwhelming reaction was – ‘this is unfair, how are you going to get it resolved?’"

Members of both unions took the action against an imposed pay offer worth 1.8% for 2007 and 1.3% for 2008. NML admits it is a low-pay employer and that it has deliberately sought real savings from the pay bill to balance its books.

Hammond said unions called on NML to re-engage with staff and enter new talks on pay. "The museum should take seriously its responsibility to the heritage sector. It needs professional staff on professional levels of pay to deliver that commitment."

Alyson Pollard, Prospect branch secretary at the museum, said she was delighted at the public response. "Many visitors have refused to go in and just turned away. Others said the museum’s behaviour is plain arrogance.

"We have never been on strike in Liverpool before. Our people are committed to their work and it takes a lot to get them out of their offices and on to the street. That they have done so is a measure of the upset management has provoked."

In London, museum staff met Robert Wareing, MP for Liverpool West Derby, to lobby for support. Mr Wareing has put down an Early Day Motion, which has already attracted support from nine MPs, calling on NML to re-enter talks on pay with unions.